feat(client): 库存列表收尾——副标/toolbar 间距/移动端 golden

- 副标（还原原型 .head .sub）：KPI 上方「共 N 个商品 · 数据实时」(千分位)
- toolbar 间距 token 化：搜索框对齐原型 240，间隔走 AppDims.sp2/sp3
- 移动端 golden：窄屏(390)卡片流路径 ×三主题入回归闸
- 顺带修 DataTableCard 分页条窄屏横向溢出（mobile 隐藏每页选择器，
  golden 闸抓出的预存 bug）

analyze 0 error · flutter test +175（库存桌面/移动各 3 golden 全过）。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/test/golden/inventory_list_golden_test.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:jiu_client/core/models/page_result.dart';
@@ -70,20 +71,32 @@ class _FakeSpecNotifier extends ProductSpecListNotifier {
   Future<List<ProductSpecOption>> build() async => const [];
 }
 
-void main() {
-  TestWidgetsFlutterBinding.ensureInitialized();
-  SharedPreferences.setMockInitialValues({});
-
-  goldenAcrossThemes(
-    'inventory list 整屏',
-    goldenPrefix: 'inventory_list',
-    child: () => const Scaffold(body: InventoryListScreen()),
-    overrides: () => [
+List<Override> _overrides() => [
       inventoryListProvider.overrideWith(() => _FakeInvNotifier()),
       productSeriesListProvider.overrideWith(() => _FakeSeriesNotifier()),
       productSpecListProvider.overrideWith(() => _FakeSpecNotifier()),
       isReadonlyProvider.overrideWithValue(false),
-    ],
+    ];
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+  SharedPreferences.setMockInitialValues({});
+
+  // 桌面：宽屏表格路径
+  goldenAcrossThemes(
+    'inventory list 整屏(桌面)',
+    goldenPrefix: 'inventory_list',
+    child: () => const Scaffold(body: InventoryListScreen()),
+    overrides: _overrides,
     logical: const Size(1280, 900),
   );
+
+  // 移动：窄屏（<600）→ context.isMobile → MobileListCard 卡片流路径
+  goldenAcrossThemes(
+    'inventory list 整屏(移动)',
+    goldenPrefix: 'inventory_list_mobile',
+    child: () => const Scaffold(body: InventoryListScreen()),
+    overrides: _overrides,
+    logical: const Size(390, 1400),
+  );
 }